I use the British Newspaper Archive, but it is far from reliable in its character recognition, so searches for information that is actually there, can end up fruitless.
From death notices again, I can also identify a son Norman McGuffie who died on 28 May 1960 and was buried in Redburn Cemetery, tragically it was a few days after a football accident during lunchtime at his work, his reported age at death would indicate birth c. 1933/4, he left a wife and little daughter (named, but won't mention here, in case alive). Lots of family information in the death notices, for example, they indicate that John McGuffie b. 1918 married someone with the forename Phyllis, also that there was another son called Donald McGuffie.
So in no particular order, the tally of children looks like John, Alexander, Christina, Daniel, Donald, and Norman.
Again if you have access to the Belfast Telegraph archive, there are various other mentions of McGuffie which are almost certainly these same folk, eg. references to addresses, where they worked, hobbies, not a huge amount.
